Hi,
On Fri, Oct 02, 2020 at 06:59:22PM +0200, John Wood wrote:
>
> static void brute_share_stats(struct brute_stats **src,
> struct brute_stats **dst)
> {
> spin_lock(&(*src)->lock);
> refcount_inc(&(*src)->refc);
> *dst = *src;
> spin_unlock(&(*src)->lock);
> }
>
> static int brute_task_alloc(struct task_struct *task, unsigned long
> clone_flags)
> {
> struct task_struct *p_task;
> struct brute_stats **stats, **p_stats;
>
> p_task = task->real_parent; /////////// <----
> if (unlikely(!p_task)) /////////// <----
> return -ESRCH;
>
> stats = brute_stats_ptr(task);
> p_stats = brute_stats_ptr(p_task); /////////// <----
>
> if (likely(*p_stats)) {
> brute_share_stats(p_stats, stats);
> return 0;
> }
>
> *stats = brute_new_stats();
> if (!*stats)
> return -ENOMEM;
>
> brute_share_stats(stats, p_stats);
> return 0;
> }
>
> This code is very untested.
Now the code is tested.
> And now my first question: how can I read the
> real_parent field in a secure way. Do I need to use an rcu_read_lock()/
> rcu_read_unlock() block? Do I need to use rcu_dereference? Do I need to
> use a read_lock(&task_list_lock)/read_unlock(&task_list_lock) block?
>
> The lines with the mark are not clear to me. Sorry.
Any help would be greatly appreciated. Thanks in advance.
Regards,
John Wood
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